This invention relates to a cutting tool of the type which comprises a body which has a seat for a cutting insert in a forward part and a channel, for the feeding of coolant to at least one nozzle. in a rear part, the channel includes a bore with orifices for inflow and outflow and which is mounted in a forward part which is exposed towards the seat in order to direct a jet of fluid towards the area of the seat, wherein the channel terminates in a cavity rearwards of said front part which communicates with the bore of the nozzle.
To cool not only the cutting insert of a cutting tool, e.g. a tool for turning. but also the workpiece which is to be machined as well as the chips which are removed from the workpiece has been known a very long time. Earlier known devices for such cooling can be divided into three different main categories, namely a first category in which coolant is fed internally through the cutting insert, a second category in which at least one jet of liquid is directed towards the area of the insert from a spray device which is separate from the actual cutting tool, as well as a third category. to which the invention belongs, and which is characterized by having a cooling fluid channel built-into the actual tool and being linked to an inflow nozzle in the tool from which a jet of fluid can be aimed towards the area of the cutting insert. Examples of the first named category of cooling devices are to be found in for example SE 7901060-9, JP 3-33005, DE 3 740 814, U.S. Pat No. 5,237,894, U.S. Pat. No. 5,346,335 and FR 2 244 590, while examples of devices in the second category are to be found in, for example, FR 1 593 553, U.S. Pat. No. 4,829,859 and U.S. Pat. No. 2,653,517. Earlier known devices belonging to the third category are known through, for example, U.S. Pat. No. 4,955 264, U.S. Pat. No. 5,148,728. U.S. Pat. No. 5 340 242 and
A fundamental aim within present day technology for chip forming metal cutting is to make it possible to use the highest possible pressure of the coolant and deliver it in the form of one or more thin jets directed mainly towards the cutting insert and the chips cut free by the cutting insert. The higher the pressure which can be used in the jet of fluid the greater will be the possibility use the jet of fluid to advantage not only for pure cooling, but also in order to mechanically influence the chips which are cut free from the workpiece more specifically with the object of breaking up the chips into as small particles as possible. Within the ranks of those skilled in the art there are differences in opinion as to what should be considered low and high pressure. Generally speaking however it should be possible to divide pressures according to the following intervals.
Low pressure less than 10 bar,
Medium pressure 10-100 bar, and
High-pressure greater than 100 bar.
In older cutting tools cooling was carried out using fluids at low pressure, whereas somewhat more modern cutting tools have worked with fluid at medium pressure. In the more recent technology fluid pressures of hundreds of bars occur. Thus, for. example, the above cited U.S. Pat. No. 5,148,728 forecasts the use of fluid pressures up to 2,800 bar.
The present invention, which belongs to the third category of cooling devices according to the above definition, is based on two fundamental pieces of knowledge regarding cooling in connection with the chip forming machining of metal, partly that the exact point of impact of the jet of fluid has a major influence on whether or not a good result is to be achieved, partly and that high pressure in the jet makes for high demands on the mechanical strength and the ability to seal against leakage of fluid in the nozzle through which the fluid is to pass and be aimed before it impinges on the insert and/or chip in the form of a jet. In the tools described in U.S. Pat. No. 4,955,264, U.S. Pat. No. 5,148,728, U.S. Pat. No. 5,340,242 and WO 96/05008 the conical shaped nozzle is firmly or immovably fixed in the tool. This means that the jet of fluid will not allow itself, under any circumstances, to be redirected to other targets once the tool has been manufactured and installed.
To make it possible to change the direction of the cooling fluid a special type of nozzle device, which is, called xe2x80x9cfish eyexe2x80x9d, by those skilled in the art, is used and this is well known. Such nozzles include a sleeve which at its one end features a thread with the help of which the sleeve can be fixed in a threaded hole in the front part which faces the cutting insert of the tool, and at its opposite end features a partially spherical seat. A ball with a through hole is inserted in this seat. after which the ball is permanently retained in the seat through plastic compression of the free end of the sleeve. In this case the ball can be rotated in relation to the seat against the effect of a frictional resistance in the border area between the ball and seat. more exactly by inserting a slender pin into the bore so that the ball can be brought to rotate to the required position of alignment by vibration.
Nozzles of the latter type can be used when the coolant is at low pressure, but at high pressure the force of impact of the fluid against the ball would be so large that there would be a clear risk that the ball would be forced out of the seat.
The present invention is aimed at eliminating the above mentioned weaknesses in the known cutting tools with cooling systems and thereby create a better cutting tool. A fundamental aim of the invention is thus to create a cutting tool which works with fluid cooling and which can work with extremely high fluid pressures and at the same time permit fine adjustment of the jet of fluid towards various required targets. more exactly with the aim of steering the chips in such a direction that they do not disturb the machining operation. An aim is even to create a cutting tool on which the adjustment of the nozzle, which shapes the jet of fluid, can be carried out in a simple manner from outside the tool without having to dismantle the tool. An additional aim is to create a cutting tool the nozzle of which is reliably sealed in respect to surrounding parts of the tool even in those cases where individual nozzles are exposed to extremely,high fluid pressures.
According to the present invention at least the basic aim is satisfied by a cutting tool wherein a nozzle is mounted in a body and aimed to eject a jet of cooling fluid toward an insert seat disposed on the body. The nozzle is arranged to be pressed against a sealing surface by pressurized cooling fluid. The direction of the jet can be adjusted by rotating the nozzle about its own longitudinal axis.